Green’s Dictionary of Slang

waddie n.

also waddy
[SE wadding, something that ‘fills in’]
(US, Western)

1. a cow-rustler, a person who steals or rebrands cattle.

[US]E. Hough Story of the Cowboy 279: A genuine rustler was called a ‘waddy,’ a name difficult to trace to its origins [DA].
[US]W.M. Raine Brand Blotters (1912) 36: I see. I’m a waddy and a thief, but you’re going to protect me for old time’s sake. That’s the play, is it?
[US]P.A. Rollins Cowboy 313: The movement had also militant apostles in the ‘waddies,’ men faithful to the illegal art of rustling.

2. a cowboy, esp. a temporary cowhand.

[US] ‘Top Hand’ in Lingenfelter et al. Songs of the Amer. West (1968) 336: He rides a fancy horse, he is a favorite man, / Can get more credit than a common waddie can [...] From the top to the bottom, he’s a bold jackass, / Waddie cowboy.
[US] in J.M. Hunter Trail Drivers of Texas (1963) I 331: A cowboy is a ‘waddy’ or ‘screw’ or ‘buckaroo.’.
[US]B. Conlon ‘Rope Meat’ in Wild West Weekly 22 Oct. [Internet] The young waddy felt the two guns poked in his back.
[US]Kerouac letter 10 July in Charters I (1995) 159: The real work of castration of steers is the work of waddies, or vaqueros in Cal.
[US]Indep. Record (Helena, MT) 9 Oct. 3/7: Other westerners might be hay waddies (hay field workers) [...].